Hive install

[stixwix]

That was me (OP) saying I think it's a RMT230 - the outer case is identical.
I do have a meter, so I guess the idea is to check that the black wires get switched to live when the thermostat cuts in and to decommission I need to connect the black wires to whichever wire is live?

 

[stem]

That was me (OP) saying I think it's a RMT230 - the outer case is identical.

Thanks! sorry, I didn't recognise you

What you say sounds about right. Terminal 4 will be the neutral and 1 and 2 will be the lives. One of the lives (should be terminal 1) will measure 230V permanently (when the heating is switched on) and the other will only measure 230V when the thermostat is turned up.

If the Blue wire is 4 is confirmed as the neutral, that should be insulated / isolated from the other wires, and the remaining wires in 1 and 2 should all be joined together.

If you can trace the thermostat cables back to the junction box, it may be possible to link them there and remove the original thermostat cables altogether.

Alternatively, if you are planing to leave the old thermostat in place, you could just move the brown wire to the same terminals as the black wires.

 

[ban-all-sheds]

So should be straight swap.

With the disclaimer that I have not tried to follow the written descriptions of which terminals on what are to be connected to where, this:

absolutely precludes a "straight swap".

That core must not continue to be used for anything other than an earth.

 

[stem]

Agreed, an earth wire shouldn't be used for anything else, as I pointed out earlier.

If you have a three port motorised valve, you will need a 'hot water off' connection and I suspect that it is the green /yellow wire, because the original installer thought (incorrectly) that it would be OK to use an earth wire as a live wire as long as they put a red sleeve on it to identify it as such.

Unfortunately whilst being wrong, I reckon about a third of the heating installations I see, have been wired (not by me I hasten to add) using an earth wire for a purpose other than it was intended.

 

[ban-all-sheds]

I'm sure they have been.

But what someone did in the past is no justification for perpetuating it. If the controls are replaced then that method of wiring must not be retained.

 

[JohnW2]

... absolutely precludes a "straight swap". ...

Whilst I agree that (although quite common) it is very bad practice, my understanding is that it is not non-compliant with BS7671 - since, as I understand it, the prohibition of over-sleeving of the ends of a G/Y-insulated conductor for use as a live conductor applies only to singles.

I therefore wonder whether "absolutely precludes" is necessarily appropriate language?

Kind Regards, John

 

[ban-all-sheds]

Whilst I agree that (although quite common) it is very bad practice, my understanding is that it is not non-compliant with BS7671 - since, as I understand it, the prohibition of over-sleeving of the ends of a G/Y-insulated conductor for use as a live conductor applies only to singles.

Indeed.

My bad, for not paying proper attention to "The bi-colour combination green-and-yellow shall be used exclusively for identification of a protective conductor and this combination shall not be used for any other purpose", which of course means you can't use G/Y to identify anything else, not that you can't override the G/Y identification and then use it for something else.



IMO it still falls foul of other things, like good workmanship, and (IIRC) a requirement for there to be a cpc at every point, and Part P, but that's in the realm of opinion, not "absolute preclusion".

 

[JohnW2]

Indeed. My bad, for not paying proper attention to "The bi-colour combination green-and-yellow shall be used exclusively for identification of a protective conductor and this combination shall not be used for any other purpose", which of course means you can't use G/Y to identify anything else, not that you can't override the G/Y identification and then use it for something else.

Indeed.

IMO it still falls foul of other things, like good workmanship, and (IIRC) a requirement for there to be a cpc at every point ...

I certainly agree with the former (although I wonder if I'm the only person prepared to admit that 'I have done it' in my time?!). As for the latter, that's also almost certainly true in this case, but it will sometimes be (as usually when I've done it') that a CPC 'gets to the point' in some other cable.

... and Part P, but that's in the realm of opinion, not "absolute preclusion".

I'm not so sure that (IF there were some other CPC 'at the point') one could argue that something fully compliant with BS7671 'fell foul of Part P'. I would also doubt that one could argue that it 'fell foul of Part P' if the only non-compliance with BS7671 was the absence of a CPC 'at that point' - since that requirement presumably relates to possible future changes in the installation, rather than having anything to do with the current safety of the installation. However, I'm pleased to hear that you don't necessary regard it as a matter of 'absolute preclusion'.

Kind Regards, John